Swimmers are being warned to stay away from part of Lake Taupō after a "fat-berg" produced by waste and wipes caused wastewater to spill into the lake.
The blockage led to wastewater bursting from under the manhole cover and running into the lake at the end of Hawai St, near Two Mile Bay.
Water samples were being tested from the area and the results of these were due tomorrow.
A temporary health warning was in place cautioning people not to swim in the area until the results of the testing were known.
Taupō District Council was assuring locals the spill did not affect the Two Mile Bay Sailing Centre - rather, the affected area was immediately around the outlet.
Council's operational services group manager Kevin Strongman called the situation both "disappointing" and "frustrating".
"We've invested around $100,000 a year on CCTV assessments of the system, and another $50,000 a year in high-pressure water cleaning to try and stop spills from happening," he said.
Strongman said the alarm was raised around 9pm yesterday.
Contractors rushed to the scene and a sucker truck was used in an attempt to recover as much of the spill as possible.
The spill comes just a week after another wastewater spill further around the lake at Acacia Bay.
A temporary health warning was put in place at the bay last Monday when issues with a stormwater pump caused a quantity of material to flow into the lake.
Strongman said the public needed to play its part to ensure the lake was kept pristine.
"Wet wipes and nappy liners should not end up in the wastewater system – they should be disposed of in the rubbish."